Chlorosilicate fluorescent material, method for producing the same, and light emitting device

ABSTRACT

Provided are a chlorosilicate fluorescent material having high light emission efficiency, a method for producing the same, and a light emitting device. In certain embodiments, the chlorosilicate fluorescent material has a chemical composition comprising Ca, Eu, Mg, Si, O, and Cl, wherein when a molar ratio of Si in 1 mol of the chemical composition is set as 4, the chlorosilicate fluorescent material comprises Ca in a molar ratio range of 7.0 or more and 7.94 or less, Eu in a molar ratio range of 0.01 or more and 1.0 or less, Ca and Eu in a total molar ratio range of 7.70 or more and 7.95 or less, Mg in a molar ratio range of 0.9 or more and 1.1 or less, and Cl in a molar ratio range of more than 1.90 and 2.00 or less.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims priority to Japanese Patent Application No.2018-201013, filed on Oct. 25, 2018, and Japanese Patent Application No.2019-188728, filed on Oct. 15, 2019, the entire disclosure of which areincorporated herein reference in their entirety.

BACKGROUND Technical Field

The present disclosure relates to a chlorosilicate fluorescent material,a method for producing the same, and a light emitting device. In thisspecification, the “fluorescent material” is used in the same meaning asa “fluorescent phosphor”.

Description of Related Art

A light emitting device that can emit light of various color phasesaccording to the principle of light mixing has been developed bycombining a light source with a wavelength conversion member capable ofemitting light of a color phase different from the color phase of thelight source as excited with the light emitted from the light source.For example, in a light emitting device including a light emittingelement such as a light emitting diode (hereinafter referred to as“LED”) in combination with fluorescent materials serving as wavelengthconverting members, each fluorescent material that emits red, green, andblue light is excited with light at a short wavelength sidecorresponding to visible light from ultraviolet light emitted from thelight emitting element, and the light in red, green, and blue, which arethree primary colors of light, can be mixed to obtain white light.

As a fluorescent material that emits light in yellow to green, forexample, US patent application publication No. 2006/0027785 discloses anEu-activated silicate fluorescent material.

Examples of the typical fluorescent material that emits green lightamong the silicate fluorescent materials may include Eu-activatedcalcium-magnesium chlorosilicate (the compositional formula is generallyrepresented by Ca₈Mg(SiO₄)₄Cl₂) (hereinafter referred to as“chlorosilicate fluorescent material”). The green fluorescent materialhas a large influence on the luminous flux of the light emitting device,and in order to enhance the luminous flux of the light emitting device,a chlorosilicate fluorescent material having higher light emissionefficiency is being demanded.

Thus, the present disclosure has an object to provide a fluorescentmaterial having high light emission efficiency, a method for producingthe same, and a light emitting device.

SUMMARY

The present disclosure includes the following embodiments.

A first embodiment of the present disclosure is a chlorosilicatefluorescent material having a chemical composition containing Ca, Eu,Mg, Si, O, and Cl, wherein when a molar ratio of Si in 1 mol of thechemical composition is set as 4, the chlorosilicate fluorescentmaterial comprises Ca in a molar ratio range of 7.0 or more and 7.94 orless, Eu in a molar ratio range of 0.01 or more and 1.0 or less, Ca andEu in a total molar ratio range of 7.70 or more and 7.95 or less, Mg ina molar ratio range of 0.9 or more and 1.1 or less, and Cl in a molarratio range of more than 1.90 and 2.00 or less.

A second embodiment of the present disclosure is a light emitting devicecontaining: a light source having a light emission peak wavelength in arange of 250 nm or more and 485 nm or less; and the chlorosilicatefluorescent material.

A third embodiment of the present disclosure is a method for producing afluorescent material including: providing a compound containing Ca, acompound containing Eu, a compound containing Mg, a compound containingSi, and a compound containing Cl such that a molar ratio of Ca is in arange of 7 or more and 8.2 or less, a molar ratio of Eu is in a range of0.01 or more and 1.1 or less, a molar ratio of Mg is in a range of 0.9or more and 1.1 or less, a total molar ratio of Ca and Eu is in a rangeof 8.05 or more and 8.25 or less, and a molar ratio of Cl is in a rangeof 2.0 or more and 3.0 or less when a molar ratio of Si in the compoundcontaining Si is set as 4; mixing the compound containing Ca, thecompound containing Eu, the compound containing Mg, the compoundcontaining Si, and the compound containing Cl to obtain a raw materialmixture; and calcining the raw material mixture to obtain achlorosilicate fluorescent material, wherein at least one of thecompound containing Eu, the compound containing Mg, and the compoundcontaining Si is an oxide, and the compound containing Cl optionallycontains Ca or Mg.

In accordance with the above embodiments, a chlorosilicate fluorescentmaterial having high light emission efficiency, a method for producingthe same, and a light emitting device, can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view showing an example of a lightemitting device according to the present disclosure.

FIG. 2 shows light emission spectra of the fluorescent materialsaccording to Example 3 and Comparative Example 1.

FIG. 3 shows light emission spectra of the fluorescent materialsaccording to Example 6 and Comparative Example 5.

DETAILED DESCRIPTION

The chlorosilicate fluorescent material, the production method, and thelight emitting device according to the present disclosure will behereunder described on the basis of embodiments. The embodimentsdescribed below are exemplifications for embodying the technical idea ofthe present disclosure, and the present disclosure is not limited to thefollowing fluorescent material, production method, and light emittingdevice. Standards according to Japanese Industrial Standard (JIS) Z8110are applied to the relations between color names and chromaticitycoordinates, the relations between wavelength ranges of light and colornames of monochromatic lights.

Fluorescent Material

The fluorescent material is a chlorosilicate fluorescent material havinga chemical composition containing Ca, Eu, Mg, Si, O, and Cl, whereinwhen a molar ratio of Si in 1 mol of the chemical composition is set as4, the chlorosilicate fluorescent material comprises Ca in a molar ratiorange of 7.0 or more and 7.94 or less, Eu in a molar ratio range of 0.01or more and 1.0 or less, Ca and Eu in a total molar ratio range of 7.70or more and 7.95 or less, Mg in a molar ratio range of 0.9 or more and1.1 or less, and Cl in a molar ratio range of more than 1.90 and 2.00 orless.

The fluorescent material is preferably a chlorosilicate fluorescentmaterial having a chemical composition represented by the followingformula (I).Ca_(x)Eu_(y)Mg_(z)Si₄O_(a)Cl_(b)  (I)

-   -   wherein a, b, x, y, and z each satisfy 7.0≤x≤7.94, 0.01≤y≤1.0,        7.70≤x+y≤7.95, 0.9≤z≤1.1, 15.6≤a≤16.1, and 1.90<b≤2.00.

In the formula (I), the parameters a, b, x, y, and z represent molarratios of an O element, a Cl element, a Ca element, an Eu element, and aMg element each constituting the chlorosilicate fluorescent material,respectively. The term “molar ratio” represents a molar amount of eachelement in 1 mol of the chemical composition of the fluorescentmaterial.

The chlorosilicate is represented by Ca₈Mg(SiO₄)₄Cl₂ as a theoreticalcomposition. In the chlorosilicate fluorescent material having achemical composition containing Ca, Eu, Mg, Si, O, and Cl, Eu is anactivating element, and it is considered that Eu is replaced with a partof the Ca site in the host crystal constituting the fluorescentmaterial. It has been presumed that, in the composition of thechlorosilicate fluorescent material, the total molar ratio of Ca and Euis preferably a value close to 8, which is the molar ratio of Ca in 1mol of the theoretical composition of the chlorosilicate, from theviewpoint of stability of the crystal structure. However, the presentinventors find out that when the total molar ratio of Ca and Eu in thechlorosilicate fluorescent material is 8, which is the molar ratio of Cain 1 mol of the theoretical composition, or a value more than 8, a dualphase of the calcium silicate is readily generated by binding Ca to thesilicate, and the light emission efficiency may be rather decreased.When the maximum value of the total molar ratio of Ca and Eu in 1 mol ofthe chemical composition of the chlorosilicate fluorescent material is7.95 or less, which is less than 8 that is the molar ratio of Ca in 1mol of the theoretical composition of the chlorosilicate, the generationof the dual phase of the calcium silicate is suppressed, and the lightemission efficiency can be increased. The chlorosilicate fluorescentmaterial contains Ca and Eu in a total molar ratio range of 7.70 or moreand 7.95 or less, preferably in a total molar ratio range of 7.80 ormore and 7.95 or less when a molar ratio of Si in 1 mol of the chemicalcomposition is set as 4. In the chlorosilicate fluorescent materialhaving a chemical composition represented by the formula (I), the totalvalue of the parameter x representing a molar ratio of Ca and theparameter y representing a molar ratio of Eu is in a range of 7.70 ormore and 7.95 or less (7.70≤x+y≤7.95), and preferably in a range of 7.80or more and 7.95 or less (7.80≤x+y≤7.95). When the total molar ratio ofCa and Eu in 1 mol of the chemical composition of the chlorosilicatefluorescent material is 7.70 or more, a stable crystal structure can bemaintained, and the light emission efficiency can be enhanced.

The chlorosilicate fluorescent material contains Cl, which constitutesthe host crystal, in a molar ratio range of more than 1.90 and 2.00 orless. When the molar ratio of Cl in the theoretical composition of thechlorosilicate is smaller than 1.90, defects may occur in the hostcrystal, and the light emission efficiency may be lowered. When thechlorosilicate fluorescent material contains Cl, which constitutes thehost crystal, in a molar ratio of more than 2.00, defects may occur inthe host crystal, and the light emission efficiency may be lowered. Forstability of the crystal structure, the chlorosilicate fluorescentmaterial contains Cl, which constitutes the host crystal, in a molarratio range of more than 1.90 and 2.00 or less, preferably in a molarratio range of 1.95 or more and less than 2.00. In the chlorosilicatefluorescent material having a chemical composition represented by theformula (I), the parameter b representing a molar ratio of Cl, whichconstitutes the host crystal, is in a range of more than 1.90 and 2.00or less (1.90<b≤2.00), and preferably in a range of 1.95 or more andless than 2.00 (1.95≤b<2.00).

In order to enhance the light emission efficiency, the chlorosilicatefluorescent material contains Ca in 1 mol of the chemical composition ina molar ratio range of 7.00 or more and 7.94 or less, and preferably ina molar ratio range of 7.20 or more and 7.90 or less, more preferably ina molar ratio range of 7.30 or more and 7.80 or less, even morepreferably in a molar ratio range of 7.40 or more and 7.70 or less. Inthe fluorescent material having a chemical composition represented bythe formula (I), the parameter x representing a molar ratio of Ca is ina range of 7.00 or more and 7.94 or less (7.00≤x≤7.94), and preferablyin a range of 7.20 or more and 7.90 or less (7.20≤x≤7.90), morepreferably in a range of 7.30 or more and 7.80 or less (7.30≤x≤7.80),even more preferably in a range of 7.40 or more and 7.70 or less(7.40≤x≤7.70).

The chlorosilicate fluorescent material contains Eu, which is anactivating element, in a molar ratio range of 0.01 or more and 1.00 orless, and preferably in a molar ratio range of 0.05 or more and 0.90 orless, more preferably in a molar ratio range of 0.10 or more and 0.80 orless, even more preferably in a molar ratio range of 0.15 or more and0.60 or less. When the chlorosilicate fluorescent material contains Eu,which is an activating element, in a molar ratio range of 0.01 or moreand 1.00 or less, the chlorosilicate fluorescent material absorbs lightemitted from the light source to excite electrons of Eu, and thewavelength of the light emitted from the light source can be convertedby the excitation energy. When the chlorosilicate fluorescent materialcontains Eu in a molar ratio range of 0.01 or more and 1.00 or less, forexample, the chlorosilicate fluorescent material can absorb lightemitted from the light source, which has a light emission peakwavelength in a range of 250 nm or more and 485 nm or less, to therebyemit light having a light emission peak wavelength in a range of 495 nmor more and 548 nm or less. In addition, when the chlorosilicatefluorescent material contains Eu in a molar ratio range of 0.01 or moreand 1.00 or less, the light emission efficiency can be enhanced, ratherthan lowering the light emission efficiency due to concentrationquenching. In the chlorosilicate fluorescent material having a chemicalcomposition represented by the formula (I), the parameter y representinga molar ratio of Eu is in a range of 0.01 or more and 1.00 or less(0.01≤y≤1.00), and preferably in a range of 0.05 or more and 0.90 orless (0.05≤y≤0.90), more preferably in a range of 0.10 or more and 0.80or less (0.10≤y≤0.80), even more preferably in a range of 0.15 or moreand 0.60 or less (0.15≤y≤0.60).

In order to obtain a stable crystal structure, the chlorosilicatefluorescent material contains Mg in 1 mol of the chemical composition ina molar ratio range of 0.90 or more and 1.10 or less, and preferably ina molar ratio range of 0.95 or more and 1.05 or less. In the fluorescentmaterial having a chemical composition represented by the formula (I),in order to obtain a stable crystal structure, the parameter zrepresenting a molar ratio of Mg in the composition is in a range of0.90 or more and 1.10 or less (0.90≤z≤1.10), and preferably in a rangeof 0.95 or more and 1.05 or less (0.95≤z≤1.05).

In order to obtain a stable crystal structure, the chlorosilicatefluorescent material contains O in 1 mol of the chemical composition ina molar ratio range of 15.60 or more and 16.10 or less, and preferablyin a molar ratio range of 15.73 or more and 16.05 or less, morepreferably in a molar ratio range of 15.78 or more and 16.00 or less. Inthe chlorosilicate fluorescent material having a chemical compositionrepresented by the formula (I), in order to obtain a stable crystalstructure, the parameter a representing a molar ratio of O in thecomposition is in a range of 15.60 or more and 16.10 or less(15.60≤a≤16.10), and preferably in a range of 15.73 or more and 16.05 orless (15.73≤a≤16.05), more preferably in a range of 15.78 or more and16.00 or less (15.78≤a≤16.00). The parameter a representing a molarratio of O in the chemical composition represented by the formula (I)can be calculated from the parameters x, y, z, and b representing amolar ratio of each element other than O, which constitutes thefluorescent material, according to the following formula (1).a=x+y+z+(4×2)−(b÷2)  (1)

The fluorescent material is preferably a fluorescent material comprisingthe chlorosilicate fluorescent material as a fluorescent material core,and at least one oxide selected from the group consisting of Al₂O₃,SiO₂, ZrO₂, and TiO₂ is adhered on the surface of the fluorescentmaterial core.

Since the chlorosilicate fluorescent material contains chlorine in thecomposition, it tends to deteriorate in a high temperature and highhumidity environment. By adhering at least one oxide selected from thegroup consisting of Al₂O₃, SiO₂, ZrO₂, and TiO₂ on the surface of thefluorescent material core comprising or composed of the chlorosilicatefluorescent material, the fluorescent material may suppressdeterioration of the surface in a high temperature and high humidityenvironment, and the durability of the light emitting device using thechlorosilicate fluorescent material can be improved.

Examples of the method for adhering at least one oxide selected from thegroup consisting of Al₂O₃, SiO₂, ZrO₂, and TiO₂ on the surface of thefluorescent material core comprising or composed of the chlorosilicatefluorescent material may include a forming method using a metalalkoxide-containing solution containing at least one metal elementselected from the group consisting of Al, Si, Zr, and Ti according to asol-gel method. In order to suppress the deterioration of thefluorescent material core, the oxide to be adhered on the surface of thefluorescent material core is preferably adhered in a film shape on thesurface of the fluorescent material core, and is more preferably adheredin a film shape on the entire surface of the fluorescent material core.

The amount of the oxide to be adhered on the surface of the fluorescentmaterial core is preferably in a range of 2 parts by mass or more and 30parts by mass or less relative to 100 parts by mass of the fluorescentmaterial core in terms of metal contained in the oxide, more preferablyin a range of 3 parts by mass or more and 25 parts by mass or less, evenmore preferably in a range of 4 parts by mass or more and 24 parts bymass or less. The amount of the oxide to be adhered on the surface ofthe fluorescent material core may be in a range of 2 parts by mass ormore and 20 parts by mass or less relative to 100 parts by mass of thefluorescent material core in terms of metal contained in the oxide, andmay be in a range of 3 parts by mass or more and 10 parts by mass orless. Specifically, the metal contained in the oxide to be adhered onthe surface of the fluorescent material core is, for example, at leastone element selected from the group consisting of Al, Si, Zr, and Ti.When the amount of the oxide to be adhered on the surface of thefluorescent material core is in a range of 2 parts by mass or more and30 parts by mass or less relative to 100 parts by mass of thefluorescent material core in terms of metal contained in the oxide, theoxide can be adhered in a film shape on the surface of the fluorescentmaterial core, so that the deterioration of the surface of thechlorosilicate fluorescent material can be suppressed even in anenvironment of high temperature and high humidity, and the durability ofthe light emitting device using the chlorosilicate fluorescent materialcan be improved. When the amount of the oxide to be adhered on thesurface of the fluorescent material core is in a range of 2 parts bymass or more and 20 parts by mass or less relative to 100 parts by massof the fluorescent material core in terms of metal contained in theoxide, a relatively thin film-shaped oxide can be adhered on the surfaceof the fluorescent material core, so that the particle diameter of thechlorosilicate fluorescent material can be reduced. By reducing theparticle diameter of the chlorosilicate fluorescent material in whichthe oxide is adhered on the surface of the fluorescent material core,the chlorosilicate fluorescent material can be unevenly distributed thelight emission side in the fluorescent member, so that the light ofwhich the wavelength is converted by the chlorosilicate fluorescentmaterial is easily extracted from the light emitting device, and therelative luminous flux of the light emitting device can be enhanced.

The particle diameter of the chlorosilicate fluorescent material ispreferably 2.0 μm or more, more preferably 4.0 μm or more, even morepreferably 5.0 μm or more; and preferably 30.0 μm or less, morepreferably 25.0 μm or less. When the particle diameter of thechlorosilicate fluorescent material is in a range of 2.0 μm or more and30.0 μm or less, the conversion efficiency of light emitted from thelight source can be more enhanced, and the light emission efficiency ofthe light emitting device using the chlorosilicate fluorescent materialcan be increased. In addition, when the particle diameter of thechlorosilicate fluorescent material is 30.0 μm or less, thehandleability of the fluorescent material is improved, and theworkability in the production process for the light emitting device canbe improved. The particle diameter of the chlorosilicate fluorescentmaterial means a particle diameter (hereinafter also referred to as“volume median diameter”) where the volume cumulative frequency from thesmall diameter side measured by a laser diffraction particle sizedistribution measuring apparatus reaches 50%. As the laser diffractionparticle size distribution measuring apparatus, a Master Sizer 3000manufactured by Malvern Instruments Ltd. can be used.

The chlorosilicate fluorescent material may contain at least one elementselected from the group consisting of Sr, Ba, and Al; and at least oneelement selected from the group consisting of Sr, Ba, and Al may becontained in a ratio of 360 ppm by mass or less relative to 100% by massof the chlorosilicate fluorescent material. Sr and Ba are elementsbelonging to the same group as Ca constituting the composition of thechlorosilicate fluorescent material and are contained in the compoundcontaining Ca which is a raw material of the chlorosilicate fluorescentmaterial, and thus Sr and Ba may be mixed in the fluorescent material.In addition, Al may be contained in the compound containing Si which isa raw material of the chlorosilicate fluorescent material and may beused as a material of a dispersion medium used in the production of thefluorescent material, and thus Al may be mixed at the time of producingthe fluorescent material. Even in the case where the chlorosilicatefluorescent material contains at least one element selected from Sr, Ba,and Al which are elements other than the element constituting thecomposition, the light emission efficiency is not lowered as long as thecontent ratio is 360 ppm by mass or less. In the case where thechlorosilicate fluorescent material contains two or more elementsselected from the group consisting of Sr, Ba, and Al, the total contentof the two or more elements may be 360 ppm by mass or less relative to100% by mass of the fluorescent material. The chlorosilicate fluorescentmaterial is able to maintain high light emission efficiency even whenthe chlorosilicate fluorescent material contains at least one elementselected from the group consisting of Sr, Ba, and Al, when the elementis in a ratio of 360 ppm by mass or less relative to 100% by mass of thechlorosilicate fluorescent material. However, the content of at leastone element selected from the group consisting of Sr, Ba, and Al in thechlorosilicate fluorescent material may be 350 ppm by mass or less, 300ppm by mass or less, or 250 ppm by mass or less.

Method For Producing Fluorescent Material

The method for producing a fluorescent material may comprise: providinga compound containing Ca, a compound containing Eu, a compoundcontaining Mg, a compound containing Si, and a compound containing Clsuch that a molar ratio of Ca is in a range of 7 or more and 8.2 orless, a molar ratio of Eu is in a range of 0.01 or more and 1.1 or less,a molar ratio of Mg is in a range of 0.9 or more and 1.1 or less, atotal molar ratio of Ca and Eu is in a range of 8.05 or more and 8.25 orless, and a molar ratio of Cl is in a range of 2.0 or more and 3.0 orless when a molar ratio of Si in the compound containing Si is set as 4;mixing each of the compound containing Ca, the compound containing Eu,the compound containing Mg, the compound containing Si, and the compoundcontaining Cl to obtain a raw material mixture; and calcining the rawmaterial mixture to obtain a chlorosilicate fluorescent material,wherein at least one of the compound containing Eu, the compoundcontaining Mg, and the compound containing Si is an oxide, and thecompound containing Cl optionally contains Ca or Mg.

Compounds

As the compound containing Ca, the compound containing Eu, and thecompound containing Mg, a halogen salt, an oxide, a carbonate, aphosphate, and a silicate or an ammonium salt containing each elementcan be used respectively. As the compound containing Si, an oxide, ahydroxide, an oxynitride compound, a nitride compound, an imidecompound, and an amide compound each containing Si can be used. Thecompound containing Cl may be a chloride containing Ca or Mg. Specificexamples of the compound containing Ca may include CaF₂, CaCl₂, andCaCO₃. Examples of the compound containing Eu may include metaleuropium, Eu₂O₃, EuN, an imide compound containing Eu, and an amidecompound containing Eu. Examples of the compound containing Mg mayinclude MgF₂, MgCl₂, MgO, and MgCO₃. Examples of the compound containingSi may include a single substance of Si, SiO₂, Si₃N₄, and Si(NH₂)₂.Examples of the compound containing Cl may include CaCl₂ and MgCl₂.

The compound containing Ca and the compound containing Eu are weighedsuch that a molar ratio of Ca is in a range of 7 or more and 8.2 orless, a molar ratio of Eu is in a range of 0.01 or more and 1.1 or less,and a total molar ratio of Ca and Eu is in a range of 8.05 or more and8.25 or less when a molar ratio of Si is set as 4. When the compoundcontaining Ca and the compound containing Eu are weighed so as to be themolar ratios in the above range, the total molar ratio of Ca and Eu inthe obtained fluorescent material can be a value close to 8 which is amolar ratio in the theoretical composition of the chlorosilicate andcannot be 8 or more. By adjusting the total molar ratio of Ca and Eu inthe obtained fluorescent material as described above, Ca is bound to thesilicate not to form the dual phase of the calcium silicate, and afluorescent material having high light emission efficiency can be thusproduced. The compound containing Ca is weighed such that a molar ratioof Ca is preferably in a range of 7.2 or more and 8.1 or less, morepreferably in a range of 7.4 or more and 8.0 or less, even morepreferably in a range of 7.5 or more and 7.9 or less when a molar ratioof Si is set as 4. The compound containing Eu is weighed such that amolar ratio of Eu is preferably in a range of 0.05 or more and 1.0 orless, more preferably in a range of 0.10 or more and 0.9 or less, evenmore preferably in a range of 0.12 or more and 0.8 or less when a molarratio of Si is set as 4. Also, the compound containing Ca and thecompound containing Eu are weighed such that a total molar ratio of Caand Eu is preferably in a range of 8.05 or more and 8.24 or less when amolar ratio of Si is set as 4.

In order to obtain a fluorescent material having a stable crystalstructure, the compound containing Mg is weighed such that a molar ratioof Mg is in a range of 0.9 or more and 1.1 or less, preferably in arange of 0.95 or more and 1.05 or less when a molar ratio of Si is setas 4.

The compound containing Cl is weighed such that a molar ratio of Cl isin a range of 2.0 or more and 3.0 or less, preferably in a range of 2.1or more and 2.8 or less, more preferably in a range of 2.2 or more and2.7 or less when a molar ratio of Si is set as 4. When a molar ratio ofCl in 1 mol of the chemical composition contained in the obtainedfluorescent material is small as 1.90 or less, defects may occur in thehost crystal of the obtained fluorescent material, and the raw materialsare readily scattered at the time of heat treating. Thus, the compoundcontaining Cl is preferably contained in a molar ratio of 2 or more inthe theoretical composition of the chlorosilicate. In the case where thecompound containing Cl contains elements other than Cl, which constitutethe chemical composition of the fluorescent material, the compoundcontaining Cl is preferably weighed such that a molar ratio of eachelement constituting the chemical composition of the fluorescentmaterial is in the above molar ratio range.

Raw Material Mixture

The weighed compounds are mixed in wet or in dry using a mixing machineto obtain a raw material mixture. As the mixing machine, a ball millwhich is generally industrially used, as well as a grinding machine sucha vibration mill, a roll mill, or a jet mill, can be used. The rawmaterials can be ground to enlarge the specific surface area. In orderto adjust the specific surface area of the particles in a certain range,the raw materials can be classified using: a wet separator such as asedimentation tank, a hydrocyclone, or a centrifugal separator; or a dryclassifier such as a cyclone or an air separator, which are generallyindustrially used.

Flux

The raw material mixture may contain a flux. When the raw materialmixture contains a flux, the reaction between the raw materials can bepromoted and further the solid-phase reaction can proceed moreuniformly, and therefore a calcined product to be used for obtaining afluorescent material having more excellent light emissioncharacteristics can be produced. For example, when the heat treatmenttemperature for providing the calcined product is in a range of 1,000°C. or more and 1,250° C. or less, and when a halide is used as the flux,it may be considered that the temperature in the range is substantiallythe same as the formation temperature of the halide liquid phase, sothat the solid-phase reaction between the raw materials can proceed moreuniformly. As the halide to be used as the flux, a rare earth metal suchas cerium or europium, a chloride or fluoride of alkali metal, can beused. The flux can be added as a part of the raw materials of thefluorescent material by adjusting the elemental ratio of the cationcontained in the flux to be a composition of the desired calcinedproduct, or the flux can be added thereto after blending the rawmaterials to be a composition of the desired calcined product.

The flux component promotes reactivity, but when the amount of the fluxcontained in the raw material mixture is too large, the light emissionefficiency of the obtained fluorescent material may be lowered.Therefore, for example, the content of the flux in the raw materialmixture is preferably 10% by mass or less, more preferably 5% by mass orless.

Calcination

The raw material mixture may be placed in a crucible or a boat made ofSiC, quartz, alumina, BN or the like, and calcined in a furnace. Bycalcining the raw material mixture, a powdery calcined product can beobtained.

A calcination temperature at which calcining the raw material mixture isperformed is preferably in a range of 1,000° C. or more and 1,300° C. orless, more preferably in a range of 1,100° C. or more and 1,250° C. orless. When the calcination temperature is in a range of 1,000° C. ormore and 1,300° C. or less, a calcined product having a chemicalcomposition containing Ca, Eu, Mg, Si, O, and Cl may be obtained withoutbeing decomposed by too high calcination temperature. In thecalcination, a second calcination may be performed after performing afirst calcination, or a plurality of calcinations may be performed.

The time of the single calcination is preferably in a range of 1 hour ormore and 30 hours or less. In the single calcination, the calcinationcan be performed by changing the temperature stepwise. For example, thecalcination may be performed in two-stage calcination (multistagecalcination) in such a manner that the first-stage calcination isperformed at a temperature in a range of 800° C. or more and 1,000° C.or less, then the temperature is gradually increased, and thesecond-stage calcination is performed at a temperature in a range of1,000° C. or more and 1,300° C. or less.

The calcination of the raw material mixture is preferably performed in areducing nitrogen atmosphere. The calcination atmosphere is morepreferably a reducing nitrogen atmosphere containing hydrogen gas. Thecalcination atmosphere may also be a reducing atmosphere using a solidcarbon in an air atmosphere.

By calcining the raw material mixture in an atmosphere having a highreducing power, such as a reducing atmosphere containing hydrogen andnitrogen, a calcined product for providing a chlorosilicate fluorescentmaterial having high light emission efficiency and capable of emittinggreen light can be produced. The calcined product that is calcined in anatmosphere having a high reducing power has high light emissionefficiency because the content ratio of Eu²⁺ contained in the calcinedproduct increases. The divalent Eu is readily oxidized into a trivalentEu, but by calcining the raw material mixture in a highly-reducingatmosphere containing hydrogen and nitrogen, Eu³⁺ contained in thecalcined product is reduced into Eu²⁺. Therefore, the content ratio ofEu²⁺ contained in the calcined product increases, and a fluorescentmaterial having high light emission efficiency can be produced.

Post-Treatment After Calcining

The calcined product may be subjected to post-treatments such asgrinding, dispersion, solid-liquid separation, and drying. Thesolid-liquid separation can be performed according to an ordinaryindustrial method such as filtration, suction filtration, pressurefiltration, centrifugation, or decantation. The drying can be performedusing an ordinary industrial apparatus such as a vacuum drier, a hot airheating drier, a conical drier, or a rotary evaporator. A powderyfluorescent material can be produced by subjecting the calcined productto the post-treatments as required.

Adhesion of Oxide

The obtained chlorosilicate fluorescent material used as a fluorescentmaterial core may be brought into contact with a metalalkoxide-containing solution containing at least one element selectedfrom the group consisting of Al, Si, Zr, and Ti for hydrolysis of themetal alkoxide followed by polycondensation, so that an oxide containingat least one metal selected from the group consisting of Al, Si, Zr, andTi may be adhered thereon. It is preferable that at least one oxideselected from the group consisting of Al₂O₃, SiO₂, ZrO₂, and TiO₂ isadhered on the fluorescent material core according to a sol-gel method.When at least one oxide selected from the group consisting of Al₂O₃,SiO₂, ZrO₂, and TiO₂ is adhered, preferably in a film form, on thefluorescent material core composed of the chlorosilicate fluorescentmaterial. Thereby, the film-shaped oxide may function as a protectivefilm to suppress the deterioration of the fluorescent material due tothe external environment, and the durability of a light emitting deviceusing the fluorescent material may be thus improved.

The metal alkoxide is preferably a silane compound having 2 or morealkoxyl groups, and specific examples thereof may includemethyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane,ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane,tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, titaniumtetraprop oxide, titanium tetrabutoxide, aluminum triethoxide, aluminumtripropoxide, aluminum tributoxide, zirconium tetrapropoxide, andzirconium tetrabutoxide. In consideration of workability and easyavailability, the metal alkoxide is preferably tetraethoxysilane.

The metal alkoxide-containing solution preferably contains an organicsolvent in consideration of workability.

The organic solvent contained in the metal alkoxide-containing solutionis preferably a polar organic solvent, and examples thereof may includeethyl acetate, tetrahydrofuran, N,N-diethylformamide, dimethylsulfoxide, alcohols having a linear or branched alkyl group with 1 to 8carbon atoms, carboxylic acids such as formic acid and acetic acid, andketones such as acetone. The polar organic solvent is preferably a loweralcohol or ketone each having a linear or branched alkyl group with 1 to3 carbon atoms. The polar organic solvent is more preferably ethanol orketone having a relative permittivity of 18 to 33. Specifically, thesolvent is more preferably at least one selected from the groupconsisting of methanol (relative permittivity of 33), ethanol (relativepermittivity of 24), 1-propanol (relative permittivity of 20),2-propanol (relative permittivity of 18), and acetone (relativepermittivity of 21). When the metal alkoxide-containing solutioncontains an acid or alkali catalyst, the hydrolysis rate of the metalalkoxide can be accelerated. Examples of the acid or alkali solution tobe the catalyst may include a hydrochloric acid solution and an ammoniasolution.

The powdery chlorosilicate fluorescent material may be brought intocontact with the metal alkoxide-containing solution for hydrolysis ofthe metal alkoxide followed by polycondensation, so that at least oneoxide selected from the group consisting of Al₂O₃, SiO₂, ZrO₂, and TiO₂is adhered thereon as a main component. For example, in the case wherethe metal alkoxide is tetraethoxysilane (Si(OC₂H₅)₄), the calcinedproduct is brought into contact with a solution containingtetraethoxysilane (Si(OC₂H₅)₄) and the tetraethoxysilane is hydrolyzedto form orthosilicic acid (Si(OH)₄), and then dehydration reaction runson through polycondensation of the orthosilicic acid (Si(OH)₄), so thata silica (SiO₂) is adhered in a film form on the surface of thefluorescent material core as a main component.

Light Emitting Device

A light emitting device using the fluorescent material as a constituentelement of a wavelength converting member will be described. The lightemitting device according to the present disclosure contains achlorosilicate fluorescent material and an excitation light source. Thelight source has a light emission peak wavelength in a range of 250 nmor more and 485 nm or less. The chlorosilicate fluorescent materialpreferably has a light emission peak wavelength in a range of 495 nm ormore and 548 nm or less by absorbing light emitted from the lightsource.

One example of the light emitting device will be described withreference to the drawing. FIG. 1 is a schematic cross-sectional viewshowing an example of the light emitting device.

A light emitting device 100 is provided with a molded body 40 having arecessed part, a light emitting element 10 serving as a light source,and a fluorescent member 50 to cover the light emitting element 10. Themolded body 40 is composed of a first lead 20 and a second lead 30 asintegrally molded with a resin part 42 containing a thermoplastic resinor a thermosetting resin. In the molded body 40, the first lead 20 andthe second lead 30 each constituting the bottom surface of the recessedpart are disposed, and the resin part 42 constituting the side surfaceof the recessed part is disposed. The light emitting element 10 ismounted on the bottom surface of the recessed part of the molded body40. The light emitting element 10 has a pair of positive and negativeelectrodes, and the pair of positive and negative electrodes each areindividually electrically connected to the first lead 20 and the secondlead 30 via wires 60. The light emitting element 10 is covered with thefluorescent member 50. The fluorescent member 50 contains a fluorescentmaterial 70 that undergoes wavelength conversion of light emitted fromthe light emitting element 10. The fluorescent material 70 contains achlorosilicate fluorescent material as a first fluorescent material 71,and may contain a second fluorescent material 72 and a third fluorescentmaterial 73 each having a light emission peak wavelength range differentfrom that of the first fluorescent material. The fluorescent member 50functions not only as a wavelength converting member but also as amember for protecting the light emitting element 10, the firstfluorescent material 71, the second fluorescent material 72, and thethird fluorescent material 73 from an external environment. The lightemitting device 100 emits light upon receiving external power via thefirst lead 20 and the second lead 30.

The method for producing a light emitting device preferably includes:preparing a molded body having a recessed part, which is integrallymolded with a first lead, a second lead, and a resin part; mounting alight emitting element on the first lead and electrically connecting apair of electrodes of the light emitting element to the first lead andthe second lead respectively using wires; and disposing a resincomposition containing a first fluorescent material, optionally a secondfluorescent material and a third fluorescent material, and a resin inthe recessed part of the molded body and curing the resin composition toform a fluorescent member. The resin composition can be disposed in therecessed part of the molded body by dropping (potting) using, forexample, an ejection apparatus (dispenser).

Light Emitting Element

For the light source, a light emitting element can be used. The lightemitting element emits light in a wavelength range of 250 nm or more and485 nm or less. In order to efficiently excite the fluorescent material,the light emitting element preferably has a light emission peakwavelength in a range of 300 nm or more and 480 nm or less, morepreferably in a range of 350 nm or more and 480 nm or less. When thelight emitting element is used as the excitation light source, a lightemitting device capable of emitting a mixed color light of light fromthe light emitting element and fluorescence from the fluorescentmaterial, which has a desired color temperature and color tone, can beconstituted.

The full width at half maximum of the light emission peak in the lightemission spectrum of the light emitting element may be, for example, 30nm or less. For the light emitting element, a semiconductor lightemitting element is preferably used. Using a semiconductor lightemitting element as a light source enables a high efficiency stablelight emitting device that has high linearity of output relative toinput and is resistant to mechanical shock to be obtained. For example,a semiconductor light emitting element using a nitride-basedsemiconductor (In_(X)Al_(Y)Ga_(1-X-Y)N, 0≤X, 0≤Y, X+Y≤1) can be used asthe semiconductor light emitting element. The full width at half maximumof the fluorescent material and the full width at half maximum of thelight emitting element means a wavelength width of the light emissionspectrum showing a value of 50% of the maximum light emission intensityin the light emission spectrum.

Fluorescent Member

First Fluorescent Material

The fluorescent member contains a chlorosilicate fluorescent material asa first fluorescent material, and may contain a second fluorescentmaterial and a third fluorescent material each having a light emissionpeak wavelength range different from that of the first fluorescentmaterial. The first fluorescent material is preferably a fluorescentmaterial comprising a fluorescent material core composed of achlorosilicate fluorescent material, which has durability even in anenvironment of high temperature and high humidity, wherein at least oneoxide selected from the group consisting of Al₂O₃, SiO₂, ZrO₂, and TiO₂is adhered on the surface of the fluorescent material core.

The first fluorescent material can be, for example, contained in thefluorescent member that covers the light source to constitute the lightemitting device. In the light emitting device where the light source iscovered with the fluorescent member containing the first fluorescentmaterial, a part of light emitted from the light source is absorbed bythe first fluorescent material, and is emitted by being converted intogreen light having a light emission peak wavelength in a range of 495 nmor more and 548 nm or less. When the light source capable of emittinglight in a wavelength range of 250 nm or more and 485 nm or less isused, a part of the emitted light can be more effectively utilized bythe fluorescent material in the fluorescent member.

The amount of the first fluorescent material contained in the lightemitting device may be appropriately selected in accordance with thecolor to be finally obtained. The content of the first fluorescentmaterial can be in a range of 2 parts by mass or more and 200 parts bymass or less relative to 100 parts by mass of the resin contained in thefluorescent member, may be in a range of 10 parts by mass or more and100 parts by mass or less, and is preferably in a range of 10 parts bymass or more and 50 parts by mass or less.

The fluorescent member may contain a second fluorescent material and athird fluorescent material each having a light emission peak wavelengthrange different from that of the first fluorescent material. Forexample, when the light emitting device appropriately comprises a lightemitting element capable of emitting blue light, a first fluorescentmaterial to be excited with the light, and optionally a secondfluorescent material and a third fluorescent material, a mixed colorlight having a desired color temperature and having a broad colorreproducibility range or a high color rendering property can be emitted.

Second Fluorescent Material

As the second fluorescent material, for example, a yellow fluorescentmaterial having a light emission peak wavelength in a range of 530 nm ormore and 580 nm or less by absorbing light emitted from the light sourcein a wavelength range of 250 nm or more and 485 nm or less can be used.Examples of the second fluorescent material may include fluorescentmaterials represented by (Ca,Sr,Ba)₂SiO₄:Eu,Si_(6-w)Al_(w)O_(w)N_(8-w):Eu (0<w≤4.2), (Sr,Ba,Ca)Ga₂S₄:Eu,(La,Y,Gd,Lu)₃(Ga,Al)₅O₁₂:Ce, (La,Y,Gd)₃Si₆N₁₁:Ce, Ca₃Sc₂Si₃O₁₂:Ce,CaSc₄O₄:Ce, K₂(Si,Ge,Ti)F₆:Mn, (Ca,Sr,Ba)₂Si₅N₈:Eu, and(Sr,Ba,Ca)₈MgSi₄O₁₆(F,Cl,Br)₂:Eu (chlorosilicate fluorescent materialshaving compositions different from that of the first fluorescentmaterial).

In the composition representing a fluorescent material, plural elementssectioned by the comma (,) in parentheses mean that at least one ofthese plural elements is contained in the composition. The pluralelements sectioned by the comma (,) in parentheses in the compositionmean that at least one element selected from the plural elements thussectioned by the comma is contained in the composition, and two or moreelements selected from the plural elements may be contained therein incombination. In the composition representing a fluorescent material, thepart before the colon (:) represents elements constituting a hostcrystal and molar ratios of these, and the part after the colon (:)represents an activating element.

The amount of the second fluorescent material contained in the lightemitting device may be appropriately selected in accordance with thecolor to be finally obtained. The content of the second fluorescentmaterial contained in the fluorescent member can be in a range of 1 partby mass or more and 150 parts by mass or less relative to 100 parts bymass of the resin contained in the fluorescent member, may be in a rangeof 1 part by mass or more and 100 parts by mass or less, and ispreferably in a range of 2 parts by mass or more and 50 parts by mass orless.

Third Fluorescent Material

As the third fluorescent material, for example, a yellow fluorescentmaterial having a light emission peak wavelength in a range of 610 nm ormore and 790 nm or less by absorbing light emitted from the light sourcein a wavelength range of 250 nm or more and 485 nm or less can be used.Examples of the third fluorescent material may include CaAlSiN₃:Eu,(Ca,Sr)AlSiN₃:Eu, (Sr,Ca)LiAl₃N₄:Eu, (Ca,Sr)₂Mg₂Li₂Si₂N₆:Eu, and3.5MgO·0.5MgF₂·GeO₂:Mn.

The amount of the third fluorescent material contained in the lightemitting device may be appropriately selected in accordance with thecolor to be finally obtained. The content of the third fluorescentmaterial contained in the fluorescent member can be in a range of 1 partby mass or more and 150 parts by mass or less relative to 100 parts bymass of the resin contained in the fluorescent member, may be in a rangeof 1 part by mass or more and 100 parts by mass or less, and ispreferably in a range of 2 parts by mass or more and 50 parts by mass orless.

The total content of the fluorescent materials in the fluorescent membercan be, for example, in a range of 5 parts by mass or more and 300 partsby mass or less relative to 100 parts by mass of the resin, and ispreferably in a range of 10 parts by mass or more and 250 parts by massor less, more preferably in a range of 15 parts by mass or more and 230parts by mass or less, even more preferably in a range of 15 parts bymass or more and 200 parts by mass or less. When the total content ofthe fluorescent materials in the fluorescent member falls within theabove range, the wavelength of light emitted from the light emittingelement can be efficiently converted by the fluorescent materials.

Examples of the resin constituting the fluorescent member may includethermosetting resins such as a silicone resin, an epoxy resin, anepoxy-modified silicone resin, and a modified silicone resin.

The fluorescent member may further contain a filler, a light diffusingmaterial in addition to the resin and the fluorescent material. Forexample, when containing a filler or a light diffusing material, thedirectionality from the light emitting element is relaxed, so that theviewing angle can be enlarged. Examples of the filler or the lightdiffusing material may include silica, titanium oxide, zinc oxide,zirconium oxide, and alumina. In the case where the fluorescent membercontains a filler or a light diffusing material, the content of thefiller or the light diffusing material can be, for example, in a rangeof 1 part by mass or more and 20 parts by mass or less relative to 100parts by mass of the resin.

EXAMPLES

The present disclosure is hereunder specifically described by referenceto the following Examples. The present disclosure is not limited tothese Examples.

Example 1

CaCO₃, Eu₂O₃, MgO, SiO₂, and CaCl₂ were used as raw materials. These rawmaterials were weighed as a charged amount such that a molar ratio ofeach element was Ca:Eu:Mg:Si:Cl=7.75:0.3:1:4:2.5 when a molar ratio ofSi was set as 4, and then mixed to obtain a raw material mixture. Themolar ratio of each element was calculated by modifying the purity ofeach raw material to 100% by mass. Since Cl scatters during calcining,Cl was blended in an amount larger than a value of the desiredcomposition ratio (molar ratio). The raw material mixture was filledinto an alumina boat and then calcined at 1,170° C. for 12 hours in ahydrogen nitrogen atmosphere which is a reducing atmosphere to obtain acalcined product having a composition represented byCa_(7.55)Eu_(0.20)Mg_(0.98)Si₄O_(15.79)Cl_(1.91). Since the particles ofthe obtained calcined product were sintered together, the obtainedcalcined product was ground with alumina beads and subjected to wetdispersion followed by sieve classification to eliminate coarseparticles and fine particles, thereby obtaining a chlorosilicatefluorescent material powder.

Examples 2 to 5 and Comparative Examples 1 to 3

Using the same raw materials as in Example 1, a chlorosilicatefluorescent material powder in each of Examples and Comparative Exampleswas obtained in the same manner as in Example 1 except that, as acharged amount of the raw materials, Ca, Eu, Mg, Si, and Cl were weighedso as to be the charged molar ratios shown in Table 1 when a molar ratioof Si was set as 4.

Comparative Example 4

Using the same raw materials as in Example 1, a chlorosilicatefluorescent material powder in Comparative Example 4 was obtained in thesame manner as in Example 1 except that, as a charged amount of the rawmaterials, Ca, Eu, Mg, Si, and Cl were weighed so as to be the chargedmolar ratios shown in Table 1 when a molar ratio of Si was set as 4.

TABLE 1 Charged Molar Ratio Ca Eu Mg Si Cl Comparative 7.70 0.30 1.004.00 2.50 Example 1 Example 1 7.75 0.30 1.00 4.00 2.50 Example 2 7.800.31 1.00 4.00 2.50 Example 3 7.85 0.31 1.00 4.00 2.50 Example 4 7.900.31 1.00 4.00 2.50 Comparative 7.95 0.31 1.00 4.00 2.50 Example 2Comparative 7.50 0.50 1.00 4.00 2.50 Example 3 Example 5 7.60 0.51 1.004.00 2.50 Comparative 8.50 0.50 1.00 4.00 3.00 Example 4

Evaluation Light Emission Characteristics

The light emission characteristics of each of the obtained fluorescentmaterials were measured. As for the light emission characteristics ofeach of the fluorescent materials, using a fluorospectrophotometer(QE-2000, manufactured by Otsuka Electronics Co., Ltd.), eachfluorescent material was irradiated with light having an excitationwavelength of 450 nm to measure the light emission spectrum thereof atroom temperature (25° C.±5° C.). FIG. 2 is a diagram showing the lightemission spectra of the fluorescent materials according to Example 3 andComparative Example 1. The light emission peak wavelength λp (nm) andthe internal quantum efficiency (%) were determined from the obtainedlight emission spectrum. The internal quantum efficiency (%) wascalculated by dividing the number of light emitting quantum (%) by thenumber of light absorbing quantum (%). The results are shown in Table 2.

Compositional Analysis

Each of the obtained chlorosilicate fluorescent materials was subjectedto compositional analysis. Using an inductively coupled plasma-atomicemission spectrometer (ICP-AES) (Optima 8300, manufactured by PerkinElmer, Inc.), the molar ratios of the elements of Ca, Mg, Si, and Eu ineach of the chlorosilicate fluorescent materials were measured. Themolar ratio of the Cl element in each of the chlorosilicate fluorescentmaterials was measured using a potentiometric titrator (AT-500N,manufactured by Kyoto Electronics Manufacturing Co., Ltd.). In thecomposition of each of the fluorescent materials, the molar ratio ofeach element other than Si was calculated based on the molar ratio of Siof 4. The results are shown in Table 2 as “analyzed molar ratios”.

Particle Diameter

The particle diameter (volume median diameter) of each of the obtainedchlorosilicate fluorescent materials at a cumulative volume frequency of50% from the small-diameter side was measured using a laser diffractionparticle size distribution measuring apparatus (product name: MasterSizer 3000, manufactured by Malvern Instruments Ltd.). The results areshown in Table 2.

TABLE 2 Light Volume Emission Median Peak Internal Diameter WavelengthQuantum Analyzed Molar Ratio D50 λp Efficiency Ca Eu Mg Si O Cl Ca + Eu(μm) (nm) (%) x y z — a b x + y Comparative 13.5 515 90.4 7.51 0.22 0.984.00 15.77 1.89 7.73 Example 1 Example 1 12.1 516 91.6 7.55 0.20 0.984.00 15.79 1.91 7.76 Example 2 12.2 515 92.9 7.69 0.21 0.99 4.00 15.921.95 7.90 Example 3 11.4 516 93.4 7.67 0.22 1.01 4.00 15.91 1.99 7.89Example 4 11.2 514 91.5 7.66 0.21 1.00 4.00 15.87 2.00 7.87 Comparative12.2 514 90.4 7.67 0.22 1.01 4.00 15.89 2.01 7.89 Example 2 Comparative15.3 521 85.4 7.36 0.42 0.99 4.00 15.84 1.86 7.78 Example 3 Example 512.2 521 87.0 7.42 0.42 0.99 4.00 15.86 1.93 7.84 Comparative 46.5 51630.0 7.67 0.30 1.09 4.00 16.07 1.97 7.97 Example 4

The internal quantum efficiency of the fluorescent material in each ofExamples 1 to 4, which had a light emission peak wavelength of 514 to516 nm, was higher than that of the fluorescent material in each ofComparative Examples 1 and 2, which had a light emission peak wavelengthof 514 to 515 nm. In the fluorescent material in each of Examples 1 to4, the total value of the parameter x representing a molar ratio of Caand the parameter y representing a molar ratio of Eu was in a range of7.70 or more and 7.95 or less (7.70≤x+y≤7.95). Thus, it is presumed thatthe generation of the dual phase of the calcium silicate was suppressed,and as a result, the internal quantum efficiency was increased. Also, inthe fluorescent material in each of Examples 1 to 4, the value of theparameter b representing a molar ratio of Cl was in a range of more than1.90 and 2.00 or less (1.90<b≤2.00). Thus, it is presumed that thenumber of defects contained in the host crystal was small, and as aresult, the internal quantum efficiency was increased. Accordingly, thefluorescent material in each of Examples 1 to 4 had higher conversionefficiency of the light emitted from the light source than that of thefluorescent material in each of Comparative Examples 1 and 2.

The internal quantum efficiency of the fluorescent material in Example5, which had a light emission peak wavelength of 521 nm, was higher thanthat of the fluorescent material in Comparative Example 3, which had thesame molar ratio of Eu and light emission peak wavelength. In thefluorescent material in Example 5, the total value of the parameter xrepresenting a molar ratio of Ca and the parameter y representing amolar ratio of Eu was in a range of 7.70 or more and 7.95 or less(7.70≤x+y≤7.95). Thus, it is presumed that the generation of the dualphase of the calcium silicate was suppressed, and as a result, theinternal quantum efficiency was increased. Also, in the fluorescentmaterial in Example 5, the value of the parameter b representing a molarratio of Cl was in a range of more than 1.90 and 2.00 or less(1.90<b≤2.00). Thus, it is presumed that the number of defects containedin the host crystal was small, and as a result, the internal quantumefficiency was increased. Accordingly, the fluorescent material inExample 5 had higher conversion efficiency of the light emitted from thelight source than that of the fluorescent material in ComparativeExample 3.

In the fluorescent material in Comparative Example 4, the total value ofthe parameter x representing a molar ratio of Ca and the parameter yrepresenting a molar ratio of Eu was more than 7.95. Thus, it ispresumed that the generation of the dual phase of the calcium silicatewas not suppressed, and as a result, the light emission efficiency inComparative Example 4 was much lower than that in Comparative Example 1.

As shown in FIG. 2 , even in the light emission spectrum, the lightemission intensity at the light emission peak wavelength of thefluorescent material in Example 3 was higher than that of thefluorescent material in Comparative Example 1.

Measurement of Sr, Ba, and Al

As for the fluorescent material in Example 3, the contents of Sr, Ba,and Al in the fluorescent material were measured using the same methodas the above compositional analysis. The results are shown in Table 3.

TABLE 3 Mass ppm Sr Ba Al Example 3 97 1 140

In the fluorescent material in Example 3, the total amount of theseelements was 360 ppm by mass or less even in the case where Sr, Ba, andAl were contained, and the light emission efficiency of the fluorescentmaterial in Example 3 was higher than that of the fluorescent materialin each of Comparative Examples 1 and 2. From the results, in thechlorosilicate fluorescent material having a chemical compositionrepresented by the formula (I), even in the case where at least oneelement selected from Sr, Ba, and Al, which were elements other than theelements constituting the composition, was contained, it could beconfirmed that the light emission efficiency was not lowered as long asthe content ratio was 360 ppm by mass or less.

Example 6

Using the chlorosilicate fluorescent material in Example 3 as afluorescent material core, SiO₂ was adhered in a film form on thesurface of the fluorescent material core as a main component. Relativeto 100 g of the fluorescent material core, 180 ml of ethanol, 3.3 ml ofan aqueous solution containing 3% by mass of ammonium chloride, 3.3 mlof an aqueous solution containing 3% by mass of calcium chloride, and 30ml of ammonia water containing 18% by mass of ammonium were mixed toprepare a host liquid. The fluorescent material core was put in the hostliquid and stirred to disperse the fluorescent material core in the hostliquid, and the liquid temperature of the host liquid was maintained at45 to 55° C. A liquid containing 23.2 g of tetraethoxysilane(Si(OC₂H₅)₄) in terms of silica was prepared as a liquid A, and a liquidcontaining 22.3 ml of ammonia water containing 18% by mass of ammonium,22.3 ml of deionized water, and 1.5 ml of an aqueous solution containing3% by mass of ammonium chloride was prepared as a liquid B. Whilestirring the host liquid, the liquid A and the liquid B were dropped inthe host liquid at a dropping rate of 5.6 ml/min for liquid A and 2.2ml/min for liquid B for a dropping time of 160 minutes to obtain a mixedliquid, and after dropping the liquid A and the liquid B, the mixedliquid was stirred for 30 minutes. Thereafter, the stirring was stopped,and the fluorescent material having SiO₂ adhered on the surface of thefluorescent material core was taken out from the mixed liquid and thendried at 100° C. for 15 hours, thereby obtaining a chlorosilicatefluorescent material powder in Example 6, which had SiO₂ adhered on thesurface of the fluorescent material core.

Comparative Example 5

A chlorosilicate fluorescent material powder in Comparative Example 5,in which SiO₂ was adhered on the surface of the fluorescent materialcore, was obtained in the same manner as in Example 6 except that thechlorosilicate fluorescent material in Comparative Example 1 was used asthe fluorescent material core.

The particle diameter, the light emission peak wavelength (λp (nm)), andthe internal quantum efficiency (%) of the fluorescent material in eachof Example 6 and Comparative Example 5 were measured in the same manneras described above. The results are shown in Table 4.

TABLE 4 Light Volume Emission Fluorescent Median Peak Internal MaterialDiameter Wavelength Quantum (before SiO₂ D50 λp Efficiency adhesion)(μm) (nm) (%) Comparative Comparative 24.6 515 91.2 Example 5 Example 1Example 6 Example 3 22.2 516 93.4

The fluorescent material in Example 6 had an internal quantum efficiencyhigher than that of the fluorescent material in Comparative Example 5.As shown in FIG. 3 , the light emission spectrum of the fluorescentmaterial in Example 6 had a light emission intensity higher than that ofthe light emission spectrum in Comparative Example 5 in a wavelengthrange of 495 nm or more and 548 nm or less. From the results, even inthe case where SiO₂ was adhered on the surface of the fluorescentmaterial core in the chlorosilicate fluorescent material having achemical composition represented by the formula (I), the light emissionefficiency in Example 6 was maintained higher than that in ComparativeExample 5. As for the fluorescent material in Example 6, sincefilm-shaped SiO₂ was adhered on the surface of the fluorescent materialcore in the chlorosilicate fluorescent material having a chemicalcomposition represented by the formula (I), the film-shaped SiO₂ actedas a protective film to suppress the deterioration, so that thedurability could be increased.

Light Emitting Device Example 7

A light emitting device according to the embodiment shown in FIG. 1 wasproduced. The chlorosilicate fluorescent material in Example 6 was usedas a first fluorescent material, Y₃Al₅O₁₂:Ce was used as a secondfluorescent material, (Sr,Ca)AlSiN₃:Eu was used as a third fluorescentmaterial, and a nitride-based semiconductor light emitting elementhaving a light emission peak wavelength of 456 nm was used as a lightemitting element. A light emitting device was produced as follows: theblending amount of each fluorescent material was adjusted such that thecorrelated color temperature of light from each of the light emittingelement, the first fluorescent material, the second fluorescentmaterial, and the third fluorescent material was 5,000 K; a resincomposition containing the first fluorescent material, the secondfluorescent material, the third fluorescent material, and a siliconeresin was prepared; and a fluorescent member, in which the resincomposition was disposed by dropping (potting) the resin compositioninto the recessed part of the molded body using a dispenser and was thencured.

Comparative Example 6

A light emitting device was produced in the same manner as in Example 7except that the chlorosilicate fluorescent material in ComparativeExample 5 was used as a first fluorescent material.

Relative Luminous Flux

Using a total luminous flux measuring apparatus with an integratingsphere, the luminous flux of the light emitting device in each ofExample 7 and Comparative Example 6 was measured. The relative luminousflux of the light emitting device in Example 7 was calculated when theluminous flux of the light emitting device in Comparative Example 6 wasset as 100%. The results are shown in Table 5.

TABLE 5 Light Emitting Device Fluorescent Relative Material LuminousColor (after SiO₂ Flux Temperature adhesion) (%) (K) ComparativeComparative 100.0 5000 Example 6 Example 5 Example 7 Example 6 100.5

The relative luminous flux of the light emitting device in Example 7, atwhich the correlated color temperature was 5,000 K, was higher than thatof the light emitting device in Comparative Example 6.

Example 8

Using the chlorosilicate fluorescent material in Example 3 as afluorescent material core, a chlorosilicate fluorescent material powderin Example 8, in which SiO₂ was adhered on the surface of thefluorescent material core, was obtained in the same manner as in Example6 except that the amount of tetraethoxysilane (Si(OC₂H₅)₄) was changedto 6.8 g in terms of silica.

The particle diameter, the light emission peak wavelength (λp (nm)), andthe internal quantum efficiency (%) of the chlorosilicate fluorescentmaterial in each of Examples 6 and 8 were measured in the same manner asdescribed above. The results are shown in Table 6.

TABLE 6 Light Volume Emission Fluorescent Median Peak Internal MaterialDiameter Wavelength Quantum (before SiO₂ D50 λp Efficiency adhesion)(μm) (nm) (%) Example 6 Example 3 22.2 516 93.4 Example 8 12.6 514 93.6

The light emission peak wavelength and the internal quantum efficiencyof the chlorosilicate fluorescent material in Example 8, in which SiO₂was adhered on the surface, were substantially the same as those of thechlorosilicate fluorescent material in Example 6. On the other hand, thevolume median diameter of the chlorosilicate fluorescent material inExample 8 was smaller than that of the chlorosilicate fluorescentmaterial in Example 6.

Light Emitting Device Example 9

A light emitting device was produced in the same manner as in Example 7except that the chlorosilicate fluorescent material in Example 8 wasused as a first fluorescent material.

Relative Luminous Flux

Using a total luminous flux measuring apparatus with an integratingsphere, the luminous flux of the light emitting device in Example 9 wasmeasured. The relative luminous flux of the light emitting device inExample 9 was calculated when the luminous flux of the light emittingdevice in Comparative Example 6 was set as 100%. The results are shownin Table 7 together with the results of the light emitting device inExample 7.

TABLE 7 Light Emitting Device Fluorescent Relative Material LuminousColor (after SiO₂ Flux Temperature adhesion) (%) (K) Example 7 Example 6100.5 5000 Example 9 Example 8 101.2

The relative luminous flux of the light emitting device in Example 9, atwhich the correlated color temperature was 5,000 K, was higher than thatof the light emitting device in Example 7. The particle diameter of thechlorosilicate fluorescent material in Example 8 used in the lightemitting device in Example 9 was smaller than that of the chlorosilicatefluorescent material in Example 6 used in the light emitting device inExample 7. Thus, it is presumed that, in the light emitting device inExample 9, a large amount of the chlorosilicate fluorescent material wasunevenly distributed the upper side of the potted resin composition,that is, on the light emission side in the fluorescent member. It isalso presumed that, when a large amount of the chlorosilicatefluorescent material was unevenly distributed the light emission side inthe fluorescent member of the light emitting device, the light of whichthe wavelength was converted by the chlorosilicate fluorescent materialwas hardly absorbed into the second fluorescent material and the thirdfluorescent material. Accordingly, the relative luminous flux of thelight emitting device in Example 9 was higher than that of the lightemitting device in Example 7.

The chlorosilicate fluorescent material according to the presentdisclosure can be utilized in a light emitting device. The lightemitting device according to the present disclosure can be suitablyutilized as a light source for lighting system. In particular, the lightemitting device can be suitably utilized in light sources using a lightemitting diode as an excitation light source, such as light sources forlighting systems, LED displays, backlight sources for liquid crystals,traffic lights, lighting switches, various sensors, various indicators,and small-size strobes.

The invention claimed is:
 1. A light emitting device, comprising: alight source having a light emission peak wavelength in a range of 250nm or more and 485 nm or less; and a fluorescent member containing achlorosilicate fluorescent material as a first fluorescent material, anda second fluorescent material and a third fluorescent material eachhaving a light emission peak wavelength range different from that of thefirst fluorescent material, wherein a larger amount of thechlorosilicate fluorescent material than the second fluorescent materialand the third fluorescent material is unevenly distributed in a lightemission side in the fluorescent member, and wherein the chlorosilicatefluorescent material comprises a fluorescent material core having thechemical composition represented by the formula (I), and an oxideadhered on a surface of the fluorescent material core,Ca_(x)Eu_(y)Mg_(z)Si₄O_(a)Cl_(b)  (I) wherein a, b, x, y, and z eachsatisfy 7.0≤x≤7.94, 0.01≤y≤1.0, 7.76≤x+y≤7.90, 0.9≤z≤1.1, 15.6≤a≤16.1,and 1.90<b≤2.00, wherein the oxide is at least one oxide selected fromthe group consisting of Al₂O₃, SiO₂, ZrO₂, and TiO₂, and wherein theamount of the oxide adhered on the surface of the fluorescent materialcore is in a range of 2 parts by mass or more and 10 parts by mass orless relative to 100 parts by mass of the fluorescent material core interms of metal contained in the oxide.
 2. The light emitting deviceaccording to claim 1, wherein in the formula (I), x, y, a, and b eachsatisfy 7.80≤x+y≤7.90, 15.73≤a≤16.05, and 1.95≤b<2.00.
 3. The lightemitting device according to claim 1, wherein the chlorosilicatefluorescent material contains Al.
 4. The light emitting device accordingto claim 1, wherein the chlorosilicate fluorescent material furthercontains at least one element selected from the group consisting of Sr,Ba and Al, and wherein the at least one element is in an amount of 360ppm by mass or less relative to 100% by mass of the chlorosilicatefluorescent material.
 5. The light emitting device according to claim 1,wherein an internal quantum efficiency of the chlorosilicate fluorescentmaterial is 87.0% or more.
 6. The light emitting device according toclaim 1, wherein an internal quantum efficiency of the chlorosilicatefluorescent material is 87.0% or more and 93.4% or less.
 7. The lightemitting device according to claim 1, wherein a volume median diameterof the chlorosilicate fluorescent material is in a range of 2.0 μm ormore and less than 22.2 μm.
 8. The light emitting device according toclaim 1, wherein the fluorescent member contains a resin, and wherein acontent of the first fluorescent material is in a range of 2 parts bymass or more and 200 parts by mass or less relative to 100 parts by massof the resin contained in the fluorescent member.
 9. The light emittingdevice according to claim 1, wherein the second fluorescent materialincludes at least one of (Ca,Sr,Ba)₂SiO₄:Eu,Si_(6-w)Al_(w)O_(w)N_(8-w):Eu (0<w≤4.2), (Sr,Ba,Ca)Ga₂S₄:Eu,(La,Y,Gd,Lu)₃(Ga,Al)₅O₁₂:Ce, (La,Y,Gd)₃Si₆N₁₁:Ce, Ca₃Sc₂Si₃O₁₂:Ce,CaSc₄O₄:Ce, K₂(Si,Ge,Ti)F₆:Mn, (Ca,Sr,Ba)₂Si₅N₈:Eu, or(Sr,Ba,Ca)₈MgSi₄O₁₆(F,Cl,Br)₂:Eu.
 10. The light emitting deviceaccording to claim 1, wherein the fluorescent member contains a resin,and wherein a content of the second fluorescent material is in a rangeof 1 parts by mass or more and 150 parts by mass or less relative to 100parts by mass of the resin contained in the fluorescent member.
 11. Thelight emitting device according to claim 1, wherein the thirdfluorescent material includes at least one of CaAlSiN₃:Eu,(Ca,Sr)AlSiN₃:Eu, (Sr,Ca)LiAl₃N₄:Eu, (Ca,Sr)₂Mg₂Li₂Si₂N₆:Eu, or3.5MgO·0.5MgF₂·GeO₂:Mn.
 12. The light emitting device according to claim1, wherein the fluorescent member contains a resin, and wherein acontent of the third fluorescent material is in a range of 1 parts bymass or more and 150 parts by mass or less relative to 100 parts by massof the resin contained in the fluorescent member.